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(No Model.)

W. P. THOMAS & E. J. FRUST.

INSULATED ELECTRICAL CONDUCTOR. No. 312,405. Patented Feb. 17,1885

WITNESSESIfl M c pgl/E/ENTOR I if? (54m? fmt UNITED STATES PATENTOFFICE.

WILLIAM P. THOMAS AND EDWARD J. FROST, OF PHILADELPHIA, PA.

INSULATED ELECTRICAL CONDUCTOR.

SPECIFICATION forming part of Letters Patent No. 312,405, dated February17, 1885.-

Application filed January 16, 1883.

To all whom it may concern:

Be it known that we, WILLIAM P. THOMAS and EDWARD J. FROST, both of thecity and county of Philadelphia, in the State of Pennsylvania, haveinvented certain new and use ful improvements in Insulated fires orCables for the Transmission of Electricity.

The following is a specification of our improvements, reference beinghad to the accompanying drawings, wherein Figure l is a View inperspective of a portion of our improved cable,showingthesuccessiveinsulating coverings, and Fig. 2 is a cross section of thecable on the line 00 w of Fig. 1, the scale in both cases being somewhatenlarged.

()ur invention is intended to be used as an underground conductor, andis especially adapted for lhetransmission of powerful electric currents,such as are used for electriclighting purposes. Defects in insulation ofunderground conductors are especially due to leakage of water ormoisture, and hence various water-proof plastic materials have been usedas insulators, but the tendency of the conducting-wires to become heatedby powerful currents such as above referred to renders the useoftheseordinary waterproof plastic materials open to objections since they areliable to be melted or even burned, thus exposing the wire.

Uur invention is designed to obviate these difficulties; and to that endit consists in the combination, with the conducting-wire, of acomparatively refractory water-proof coating which is a non-conductor ofheat as well as of electricity; and, further, in a secondary insulatingcoating of more pliable water-proof material, a third covering of ahighly refractory character which is a non-conductor of heat andelec.ricity, and an outer water-proof covering of metal.

In the accompanying drawings, A represents the conducting-wire,preferably of copper. Upon this wire we apply a coating, B, ofjapan(such as is ordinarily known in commerce as baked japan) or similar gum,which is baked on at the temperature and in the manner usual injapanuing metals, care being taken that the heat shall not be so greatas to render the coating brittle. The japan ned surface is then coveredwith a coating, 0, of rubber, applied in solution and sufficiently thickto be entirely Water-proof. The cable (No model.)

thus formed is wrapped withasbestus D,which may be secured by abinding-cord, (Z, or may be plaited on, if preferred. An exterior pipeor conduit, E, of metal, is then applied, preferably by wrapping heavysheet-lead tightly upon the asbestus and soldering the edges of thesheet. The prii'n ary insulating-coating of japan is water-p roof, andsufficiently refractory not to yield unless the wire should become veryhighly heated. The pliable rubber coating is intendedespeeially toprotect the wire in case the japan should be cracked in bending the wireor from other cause, and as the interposed covering of japan is anon-condoctor ot'heat the rubber is not liable to be burned or meltedexcept under a very extraordinary increase in temperature. suchextraordinary heat occur, however, the asbestus wrapping maintains theinsulation, and being not only exceedin rly refractory, but a very lowconductor of heat, the metallic outer covering cannot become heated.

\Ve deem the application of the rubber-coating directly to the japannedsurface the most economical form in which our invention can be embodied;but as it can be applied outside of the asbestus or fibrous coating withequally good results as regards insulation we do not desire to limitourclaim to the exact order of application of these coats. The abovecombination thus produces an insulator which is in the highest degreewater-proof, refractory to heat produced by the current, pliable, anddurable.

Having thus described the nature and objects of our invention, what weclaim as new, and desire to secure by Letters Patent, is

1. The combination, with a conductingwire, of an insulating-coatingofjapan baked directly thereon, and a coating of rubber applied aroundsaid japanned surface, substantially as set forth.

2. The combination, with a conductingwire, of a japanned coating bakedthereon, a rubber coating and asbestus wrapping applied aroundthejapanned surface, and an exterior metallic pipe, substantially as andfor the purposes specified.

XVM. P. THOMAS. EWD. J. FROST. \Vitnesses:

J. \VALTER DOUGLASS, S. H. POOLE.

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